I actually had an overlay on each of the four icons that were the same size and shape as the rest of my icons ! The opacity of the overlay was set to 5% (or something low enough not to be very visible) !
But I'm sure if you have the icon without any overlay in the same dimensions as all other icons (114x114 - Default iOS icons), then it should work!
Ahh, sorry I should've written the details better >.< By dBar I meant the site dBarEvolution.co.cc which has many themes including some that aren't released elsewhere. What I did was take a certain part of one of their themes (the "device locked" image) and compile/use it as part of my lock screen
If you're looking for the theme i used, it's called LS Silence